Variable resistor construction



April 15,- 1958 M. E. BoURNs ETAL 2,831,094

VARIABLE RESISTOR CONSTRUCTION Filed Nov. 1e, 1954 VARIABLE RESISTOR CONSTRUCTION Marlan E. Bourns, Marvin E. Harrison, Robert M. Whitehorn, Richard C. Tyson, and Robert il. hiel-lor, Riverside, Calif.; said Harrison, said Whitehorn, Tyson, and said Mellor assignors to said Booms Application November 16, 1954, Serial No. 469,192

16 Claims. (Cl. lOl-48) The present invention relates to a new and improved variable resistor construction.

Despite the extremely crowded nature ci the art pertaining to variable resistor constructions there remains in the industry a continuing desire to produce new and improved variable resistors which actually constitute a decided improvement over the prior constructions. A broad object of the present invention is to provide a new and Y improved resistor construction falling into this category.`

A more specific object of the invention is to provide a variable resistor construction including a body portion, a housing surrounding at least part of said body portion so as to define a cavity between said body portion and said housing, electrically conductive means secured to said body portion soas to be generally located within said cavity, a movable member positioned within said cavity, guide means for controlling the motion of ysaid movable member with respect to said electrically conductive means, means for moving said movable member along said guide means, and Contact mounted on said movable member so as to be resiliently blessed against said electrically conductive means.

A specific object of the invention is to provide a variable resistor construction as indicated in the preceding sentence in which the means for attaching the means for moving said movable member to said movable member constitute a distinct improvement in that they permit comparatively severe misalignment of said means for rnoving said movable member without aecting the operation of said movable member. A still more specific object of the invention is to provide a variable resistor construction as indicated in the preceding paragraph wherein shield means may be incorporated so as to prevent the entrance of unwanted material into the cavity. A fur* ther object of the invention is to provide a variable resistor construction as indicated in the preceding discussion in which plug means are formed within said body portion whereby the variable resistor construction can be electrically connected to a socket by merely being plugged in in the broad manner in which a common plu g upon electrical wire is `plugged into a wall receptacle or socket.

Another object of the invention is to provide a variable resistor construction as indicatedin the second preceding paragraph wherein said electrically conductive means include two resistance means connected in parallel with `front" and 4rear ends and 26 so as toV accommodater4 in the second preceding paragraph including guide means formed within. said4 housing.

yThe exact nature of all of the constructional details of the present invention is best more fully defined by the appended claims forming a part of this description. If desired the instant invention may be brieily summarized as required by the Patent Oilice Rules as including a body portion, a housing secured to said body portion so as to define a cavity between said housing and said body portion, electrically conductive means secured to said body portion, a movable member positioned within said cavity, guide means for controlling the motion of this movable member', means for moving the movable member, andrcontact means mounted on the movable member for engaging the electrically conductive means. The exact nature of this invention is most conveniently explained with reference to the accompanying drawings in which:

Fig. l is a front-end view of a variable resistor construction of the invention;

Fig. -2 is a cross-sectional view taken at line 2--2 of Fig. l;

Fig. 3 is a backend view of the resistor shown in Fig. l;

Fig. 4 is a cross sectional View taken at line 4 4 of Pig. 2;

Pig. 5 is a cross-sectional view taken on line S-S or Pis` 2;

Fig. 6 is an isometric view of a Contact member employed; and

Fig. 7 is a diagrammatic stretch showing the electrical connectionoi various elements employed.

ln the drawings a complete variable resistor lil is shown as including a'body portion l2 of an insulating material having an elongated center section ld which isprovided Vwith a flat interior surface i6 and a curved outer peripherylil. This body portion also includes a generally cylindrical rear end 2i) which is attached to the centervsection ld as is best seen in Fig. 2 of the drawing, and which incorporates a plurality of prongs 22 projecting from the rear end 2li parallel to one another so as to constitute what may be termed plug means for attaching the complete variable resistor 1li) to a mounting socket (not shown), of these prongs is formed withy a., centrally located projection 24 within the rear end 2li so as to prevent undesired motion of these prongs Z2 .with respect to the resistor l@ during use.

The body portion l2 also includes a generally cylindrical front end 26 which is attached to the center section 1d Las is shown in Fig. 2 of the drawing. Thisy front end eincludes a centrally formed generally cylindrical opening 2S, and is adapted to be attached to a cover 3) by means of .small screws 32. The cover 30 is provided with a frontopening of approximately the same dimensions as the opening which is aligned with this opening 23. Surrounding the front opening 38 within the cover 3d there is provided a comparatively deep annular groove lli which `whenthe cover 3G is assembled as shown defines with tne adjacent surface or" the front end 25 a comparatively tlat slot having parallel side walls, this slot projecting radially from the openings and 3S. i

Secured to the body portion l2 by means of a screw 44 is a generally tubular housing d6 which completely surrounds the body portion l2 so as to in effect deline an internalk cavity is which is bounded by this housing 46, the frontand rear ends 20 and 26 and the flat inner surface 16. :The housing i6 is provided with side projections 59 extending inwardly thereof toward the cavity 48;,@Appropriate notch means 52 are provided upon the these projections when the housing 46 is placed over the body section 12. These side projections 50 are designed to engage notch means 54 formed upon a movable member 56 formed of an insulating material so as to serve as rigid or fixed guide means for this movable member as it is reciprocated within the cavity 48 by means of a shaft 58 which is attached to this movable member being moved through the openings 28 and 38, so as to prevent undesired movement or binding of the movable member 56.

A generally cylindrical shield 60 is disposed within the slot 42 surrounding the shaft 58. This shield is provided with a slanting internal wall 62 so as to accommodate the shaft 58 as this shaft is reciprocated from side to side in the opening 38 during the operation of the resistor serving to prevent the entry of dirt or other material into the cavity 48. It will be realized from an examination of Fig. 2 of the drawings that an edge 64 of the wall 62 at all times directly engages the shaft 58, and that the shield 60 is of smaller diameter than the slot 42 and that the shaft 56 is of smaller dimension that the opening 38.

The shaft 58 is attached to the movable member 56 by means which serve to constitute a ball and socket type joint or connection which serves to prevent binding in the event of misalignment of the shaft 58. This means includes a threaded bore 66 formed within the movable member 56 so as to lead to a smaller bore 68 aligned with the bore 66. With this construction a curved shoulder 70 is provided internally within the movable member 56 between the bores 66 and 68 so as to engage or carry a ball 72. This ball 72 is attached to a rod 74 projecting through the bore 68; the rod 74 is in turn connected to the shaft 58. With the construction shown the ball 72 is held in location within the threaded bore 66 by means of j a coil spring 76 biased against this ball through the use of a screw member 78 threaded within the threaded bore 66. The ball 72 and rod 74 are inserted into the bores 66, 68 through a keyhole slot in the bottom of the movable member 56, said keyhole slot comprising a narrow slot 80 having an enlarged opening 81 at one end thereof.

Attached to the movable member 56 are electrically conductive contact means which are constituted as is best seen in Fig. 6 of the drawings by means of a flat plate 82 which is secured to the movable member 56 by screws 84 passing through apertures 86 within this flat plate 82. Connected to the center portion of this plate is a resilient finger 88 provided with a bent over terminal extremity 90 so as to provide a top edge 92 which is designed to engage a base 94 of a U-shaped shorting or collector strip 96 located within a groove 98 in the surface 16 of the center section 14 of the body portion 12. With this construction the shorting strip 96 may be held in this position by means of the sides 100 of the shorting strip 96 engaging the walls of this groove 98, or by other conventional means.

Attached to the flat plate 82 on both sides of the finger 88 are short resilient projectings 102 to each of which there are welded at least two wires 104. These wires 104 are preferably tapered as indicated in Fig. 6 toward terminal bent over extremities 106. The extremities of the adjacent wires 104 are thus located immediately adjacent to one another and provide substantially continuous top edges 108 which are designed to engage resistance elements 110 disposed about supporting members 112. As is best seen in Fig. 5 of the drawings these resistance elements 110 and the supporting members 112 are secured in a conventional manner within grooves 114 formed in the surface 16 of the center section 14. It will be realized from an examination of Fig. 5 that the grooves 114 are parallel to the groove 98. With this type of construction the top edges 108 of the adjacent wires 104 engage different, but closely spaced areas of the resistance elements 110 when the movable member 56 is located anywhere along the inner surface l16. With this type of construction there is little problem with respect to intermittent Contact being made between the elements and the flat plate 82. Because of this the variable resistors incorporating this feature of the present invention are comparatively free from noise. Resistors employing this feature also have a comparatively long effective life.

During the operation of the resistor 10 it is preferred i ct the adjacent extremities of the resistance elem l ;0 tc. one another by means of wires 116 so that these resistance elements 110 operate in parallel, and are shorted through the shorting or collector strip 96 by the operation of the contact means mounted upon the n 'l member 56. This inode of connection is These wires lll-.6 are, as shown in Figs. 2 and 7 of the drawings, both connected to two of the prongs 22 in a conventional manner. The shorting stripI 96 is connected to another of these prongs 22 in a similar manner by the use of another wire 118. Other prongs 22 may be used merely to provide stability in attaching the resistor it? to a socket (not shown).

Because of the precise arrangement of electrical resistance means in parallel described above resistors inccrporating this feature operate a potentiometers having a high watt capacity. Also, because of the use of'two electrical resistors, the noise characteristics of variable resistors constructed in this manner are very good. Further because of the use of two parallel elements, the linearity of the response of the variable resistor as herein specified is comparatively great inasmuch as the nonlinearity of one of the coils 110 is apt to be compensated for by the non-linearity of the other coil.

Those skilled in the art will realize from the aforegoing description that variable resistors constructed in accordanea: with this disclosure are exceedingly ethcient for the purpose intended and are relatively incre pensive to manufacture. Obviously the present description is not restricted to the preciese constructional details illustrated in the accompanying drawings. As an example of this the wires 104 need not be round, but can have a square cross-section, an oblong cross-section, etc., so long as they provide very closely spaced areas for contacting adjacent areas of a resistance element, preferably in the same plane perpendicular to the direction of travel of these wires at any given instant. Also the shaft 58 employed can be of other than a round shape. All such modifications of this type are to be considered as part of the inventive concept insofar as they are defined in the appended claims, and are within the skill of the art.

We claim:

l. In a variable resistor having a resistance element, a movable member positioned adjacent to said resistance element, and means mounted on said movable member contacting said resistance element, the improvement which comprises: a ball movably located with respect to said movable member; and a rod projecting from said movable member attached to said ball, said rod being employed in moving said movable member.

2. I variable resistor as defined in claim l wherein said ball engages a shoulder formed within said movable member and including spring means normally holding said ball against said shoulder; and means defining an opening in said movable member for use in introducing said ball into said movable member against said shoulder.

3. A new and improved variable resistor construction which comprises: a body portion formed of an insulating material, said body portion including generally cylindrical front and rear ends and a center section connecting said ends; a tubular housing surrounding said body portion so as to define an internal cavity within said resistor, said cavity being bounded by said housing, said front and rear ends and said center section; means seamn'rnically indicated in Fig. 7 of the drawings.

curing said housing to said body portion; means defining three parallel slots within said center section; electrical resistance elements positioned within two of said slots; a shorting strip positioned within the third of said slots; means connecting said electrical resistance elements in parallel; a plurality of prongs secured to said rear end of said body portion so as to project therefrom, said prongs being adapted to be fitted Within a socket; means electrically connecting one of said resistance elements with one of said prongs; means electrically connecting said shorting strip to another of said prongs; means dening an opening within the front end of said body portion; a cover secured to said front end of said body portion; means defining an opening Within said cover, said opening in said cover being aligned with said opening within said front end; means dening a slot between said cover andsaid cover and said front end; a shaft projecting through said openings; a shield positioned within said slot, said shield engaging said shaft and being adapted to prevent the entry of dirt into said cavity; projections formed on said housing; a movable member located within said cavity, said movable mem.- ber including notches engaging said projections; means dening a threaded bore Within said movable member; Y

means defining a second bore Within said movable member, said second bore being of smaller diameter than said threaded bore and being aligned with said threaded bore; a ball positioned within said threaded bore; a rod projecting through said second bore, said rod connecting said ball and said shaft; means holding said ball adja cent to said second bore; a platey attached to said movable member; a resilient inger attached to said plate, said resilient finger engaging said shorting strip; and a plurality of ,wires secured to said plate, said wires engaging said resistance elements. r

4. ln adevice of the class described, a construction which comprises: a body portion including a surface; electrically conducting means secured to said surface; a housing secured to said body portion so as to surround said electrically conductive means and so as to define a cavity between said body portion and said housing; a movable member positioned within said cavity; guide means within said cavity for controlling the motion of said movable member, said guide means extending paral lel to said surface; means for moving said movable member along said guide means extending into said cavity; ball and socket means connecting said means for moving said movable member and said movable member; and

contact means mounted on said movable member so as toibe resiliently biased against said electrically conductive means.

5. In a device of the class described, a construction which comprises: a body portion including a surface; electrically conductive means secured to said surface; a housing secured to said body portion so as to surround said electrically conductive means and so as to define a cavity between said body portion and said housing; a movable member positioned within said cavity; guide means within said cavity for controlling the motion of said movable member, said guide means extending parallel to said surface; means defining an opening into said cavity; means dening a slot having the shape of an annular groove located around said opening into said cavity; a shaft of smaller dimension than said opening projecting through said opening into said cavity, said shaft being connected to said movable member; a cylindrical shield of smaller diameter than said slot located around said shaft so as to project into said slot; and contact means mounted on said movable member so as to be resiliently biased against said electrically conductive means.

6. A construction as dened in claim 5 wherein said shield includes a slanting internal Wall and an edge engaging said shaft.

7. in a device of the class described, a construction which comprises: a body portion including a surface; electrically conductive means secured to said surface; a housing secured to said body portion so as to surround said electrically conductive means so as to define a cavity between said body portion and said housing; a movable member positioned within said cavity, said movable member having notches formed therein; guide means for controlling the motion of said movable member eX- tending parailel to said surface, said guide means comprising projections formed on said housing, said projections engaging said notches on said movable member; means for moving said movable member along said guide means attached to said movable member; and contact means mounted on said movable member so as to be resiiient biased against said electrically conductive means.

8. A variable resistor which includes a housing; electrically conductive means mounted in said housing; fixed guide means located within said housing, said guide means comprising parallel projections extending inwardly within said housing; a movable member positioned Within said housing, said movable member including notch means engaged by such parallel projections; contact means mounted on said movable member, said contact means engaging said electrically conductive means; and means for moving said movable member.

9. A new and improved variable resistor construction which comprises: a body portion formed of an insulating material, said body portion including generally cylindrical front and rear ends and a center section connecting said ends; a tubular housing surrounding said body por tion so as to define an internal cavity within said re sistor, said cavity being bounded by said housing, said front and rear ends and said center section; means securing said housing to said body portion; means delining parallel slots within said center section; an electrical resistance element positioned Within one of said slots; a shorting strip positioned within another of said slots; a plurality of prongs secured to said rear end of said body portion so as to project therefrom, saidprongs being adapted to be fitted within a socket; means electrically connecting said resistance element with one of said prongs; means electrically connecting said shorting strip to another of said prongs; means dening an opening Within the front end of said body portion; means defining an opening Within said cover, said opening inside said cover being aligned with said opening Within said front end; means defining a slot between said cover and said front end; a shaft projecting through said openings; a shield positioned within said slot, said shield engaging said shaft and being adapted to prevent the entry of dirt into said cavity; a movable member located within said cavity; means defining a threaded bore within said movable member; means defining a second bore Within said movable member, said second bore being of smaller diameter than said threaded bore and being aligned with said threaded bore; a ball positioned within said threaded bore; a rod projecting through said second bore, said rod connecting said ball and said shaft; means holding said ball adjacent to said second bore; and contact means engaging said resistance element and said shorting strip.

l0. A new and improved variable resistor construction which comprises: a body portion formed of an insulating material, said body portion including generally cylindrical front and rear ends and a center section connecting said ends; a tubular housing surrounding said body portion so as to define an internal cavity Within said resistor, said cavity being bounded by said housing, said front and rear ends and said center section; means securing said housing to said body portion; means defining parallel slots within said center section; an electrical resistance element positioned within one of said slots; a shorting strip positioned within another of said slots; means delining an opening Within the front end of said body portion; a cover secured to said front end of said body portion;

if" means delining an opening within said cover, said opening in said cover being aligned with said opening within said front end; means defining a slot between said cover and said front end; a shaft projecting between said openings; a shield positioned within said slot, said shield engaging said shaft and being adapted to prevent the entry of dirt into said cavity; a movable member located within said cavity; means defining a threaded bore within said movable member; means defining a second bore within said movable member, said second bore being of smaller diameter than said threaded bore and being aligned with said threaded bore; a ball positioned within said threaded bore; a rod projecting through said second bore, said rod connecting said ball and said shaft; means holding said ball adjacent to said second bore; and contact means attached to said movable member, said contact means envaging said resistance element and said shorting strip.

ll. A variable resistor comprising a housing, electrically conductive means mounted within said housing, guide means located within said housing, a movable mem- 'oer slidably engaging said guide means, contact means on said movable member wiping on said electrically conductive means, and a shaft connected to said movable member by means constituting a ball and socket joint, so as to allow misalignment of said shaft with respect to said movable member, said shaft normally serving to move said movable member` l2. A variable resistor comprising a housing having a cavity therein, a resistance element mounted on said housing within said cavity, a slider movable along a path paral el to said resistance element, Contact means on said slider wiping on said resistance element, an operating shaft movable linearly along a path generally parallel to said resistance element and having one end thereof projecting into said cavity, and a ball and socket connection between said slider and said one end of said operating shaft to accommodate any misalignment between said operating shaft and said slider.

13. A variable resistor comprising a housing having a cavity therein, a resistance element mounted on said housing within said cavity, a slider movable along a path parallel to said resistance element, contact means on said slider wiping on said resistance element, an operating shaft movable linearly along a path generally parallel to said resistance element and having one end thereof projecting through an aperture in said housing into said cavity, said aperture being of larger dimension than said shaft, means defining a groove surrounding said aperture, said groove being disposed in a plane substantially perpendicular to the axis of said operating shaft, a dust shield 8 disposed within said groove and slidably movable therein, the edges of said dust shield being confined within said groove for all positions thereof, said operating shaft extending through an aperture in said dust shield, and a flexible joint connection between said one end of said operating shaft and said slider.

14. A variable resistor comprising a body having a cavity therein, a resistance element mounted on said body within said cavity, sheet metal sides extending along opposite sides of said cavity, said sheet-metal sides being bent to form inwardly projecting V-shaped ridges extending parallel to said resistance element, a slider disposed between said sheet metal sides and having notches formed in opposite sides thereof to slidably receive said V-shaped ridges, a contact on said slider wiping on said resistance element, and actuating means for moving said slider along said V-shaped ridges.

15. A variable resistor comprising a housing, a resistance element mounted on said housing, a slider supported for movement along a path parallel to said resistance el ment, said slider having a bore formed therein parallel to its line of travel, an inwardly projecting shoulder in said bore, an actuating rod projecting into said bore and having a ball on the end thereof seated on said shoulder, a spring within said bore pressing said ball against said shoulder, and contact means on said slider wiping on said resistance element.

16. In a variable resistor having a body, a resistance element mounted on said body, and a slider supported for movement along a path parallel to said resistance element, the improvement comprising a contact member having a base portion of spring sheet metal secured to said slider, a short resilient projection extending from one edge of said base portion, and a plurality of formed Contact Wires attached side-by-side to said projection, said wires having rounded contact tips arranged in a substantially straight line transverse to the longitudinal axis of said resistance element, whereby said Wires make multiple contacts with said resistance element, all at the same distance from the ends of said resistance element.

References Cited in the le of this patent UNITED STATES PATENTS 

